Method for producing a built shaft

ABSTRACT

The invention relates to a method for producing a built shaft, whereby at least one part ( 2 ), particularly a cam, is mounted on the shaft ( 1 ), particularly a camshaft, whereby the shaft ( 1 ) is inserted into an opening ( 3 ) of the part ( 2 ). Before mounting the part ( 2 ), the shaft ( 1 ) is stretched by means of a stretching and tightening device ( 7′, 7 ″) in such a manner that an original diameter (D1) in the area of at least one fastening location ( 4 ) is reduced to a diameter (D4). Afterwards, the part ( 2 ) is slid onto the shaft ( 1 ) and up to the fastening location ( 4 ) on the shaft ( 1 ). The stretching and tightening device ( 7′, 7 ″) is then loosened once again thereby enabling the diameter of the shaft ( 1 ) to enlarge once more towards its original diameter (D1). The part ( 2 ) is firmly fastened at the fastening location ( 4 ) by interference fit in both an axial as well as rotationally fixed manner.

[0001] This invention relates to a method of producing a worked shaftaccording to the preamble of Patent claim 1. In particular, thisinvention relates to a method of producing worked camshafts.

[0002] To attach cams or other components to a camshaft, which is hollowin a manner that has long-term stability, it is known that prefabricatedcams or components may be pushed onto the camshaft and to widen themhydraulically in some locations so that the cams and/or components aresecured in a torsionally fixed manner. The locally limited widening ofthe camshaft is relatively complex because special provisions arerequired (special probes, seals, etc.).

[0003] U.S. Pat. No. 5,299,881 describes a worked camshaft in which theindividual cams and the corresponding camshaft are first manufacturedcompletely in separate manufacturing steps and then the cams are pushedonto the camshaft using a special joining technique so that there is afit without play between the shaft and the cams. The prefabricated camseach have an inside bore and at least two annular zones spaced adistance apart axially, separated by at least one free space which is inthe inside bore of the cams. The space and the zones are arrangedsymmetrically with the center plane of the cams. To manufacture theworked camshaft, the individual cams are pushed onto the camshaft insuch a way that a fit is obtained between said zones and thecircumference of the shaft. There is a problem inasmuch as it isrelatively difficult and problematic to attach said shafts, inparticular when the shafts are pushed onto or over the regions to whichthey are to be secured. Furthermore, the cams have a relatively complexdesign and therefore may be manufactured only at a comparatively highcost.

[0004] The object of the present invention is to create a method ofmanufacturing a worked shaft in which the mounting of cams and/or othercomponents on the shaft can be accomplished relatively easily andinexpensively.

[0005] This object is achieved by a method of manufacturing a workedshaft having the features of Patent claim 1.

[0006] The essential advantage of the present invention is that complexhydraulic widening operations on a hollow shaft, in particular acamshaft such as those required in the related art need not be performedbecause the diameter of the shaft is reduced elastically by stretchingbefore pushing the cams and/or other components onto the shaft, so thatit is readily possible to push said cams and/or components onto theshaft. Advantageously, no complex changes need be made on the camsand/or components themselves in the implementation of the methodaccording to this invention.

[0007] The invention and the embodiments thereof are explained below inconjunction with the figures, which show:

[0008]FIG. 1 a camshaft and a cam to be mounted on it in a schematicdiagram;

[0009]FIG. 2 a method step in which the diameter of the camshaft iselastically reduced by stretching;

[0010]FIG. 3 a cam mounted on the camshaft; and

[0011]FIG. 4 a refinement of this invention.

[0012]FIG. 1 shows a shaft, preferably designed as a hollow shaft, inparticular a camshaft 1. A component to be mounted on the camshaft 1 maybe, for example, a cam 2. The cam 2 has an inner opening 3 into whichthe camshaft 1 is inserted in the manner described below for mountingthe cam 2 on the camshaft 1. The camshaft 1 has an outside diameter D1at least at the mounting site 4 where the cam 2 is to be mounted. Theinside diameter of the inner opening 3 of the cam 2 is labeled as D2.

[0013] A so-called threading area 6 having an outside diameter D3preferably smaller than the diameter D2 and also smaller than thediameter D1 is provided on an end area of the camshaft 1 so that the cam2 or other cams and/or components may be pushed onto the shaft therewith some play and/or they may already be threaded onto the shaft.

[0014] In a method step, the end areas of the camshaft 1 are preferablymounted in a stretching and chucking device 7′, 7″. This stretching andchucking device 7′, 7″ is preferably created according to FIG. 1 so thatit acts with a chucking element 7′ on the outside circumference of thecamshaft 1 and exerts a chucking force P1 on the camshaft 1. With itsother chucking element 7″, the stretching and chucking device 7′, 7″acts on the inside circumference of the hollow camshaft 1, preferablyexerting a chucking force P2 on the camshaft 1 acting in the radialdirection. Before attaching the chucking element 7″, the cams 2 and/orother components to be mounted on the camshaft 1 are pushed onto thethreading area 6.

[0015] The camshaft 1 especially preferably has an inside thread on itsside facing the chucking element 7″ onto which an outside thread of thechucking element 7″ can be screwed.

[0016] It is pointed out that the chucking element 7′ may also bedesigned according to the chucking element 7″.

[0017] The stretching and chucking device 7′, 7″ is subsequentlyoperated so that a tension is exerted on the chucked camshaft 1 so thatthe diameter D1 of the camshaft 1 is reduced to a diameter D4. It holdsthat D1>D4>D3, as also shown in FIG. 2. The chucking elements 7′ and 7″exert the stretching forces P3 and P4 thereby.

[0018] To permit the aforementioned reduction in the diameter D1 to thediameter D4 by operation of the stretching and chucking device 7′, 7″and in stretching of the camshaft 1, the camshaft 1 is made of amaterial, preferably a special steel alloy, which permits an elasticaxial elongation of the camshaft 1 due to the stretching and chuckingdevice 7′, 7″ for said reduction in diameter. In addition to the elasticdeformation, plastic deformation of the camshaft in stretching is alsopossible.

[0019] According to FIG. 2, the camshaft 2 is then pushed from thethreading area 6 onto the stretched camshaft 1 having the diameter D4and pushed in direction A to the mounting site. This is readily possiblebecause the diameter D4 is smaller than the diameter D2. The cam 2 issecured at the fastening site 4 by retaining devices, which are notshown in greater detail here, with respect to displacement in the axialdirection and in the circumferential direction.

[0020] It is also conceivable for the diameter D4 to be larger than thediameter D2 as long as it is certain that the cam 2 can then be shiftedby use of force to the mounting site 4 after the stretching operation.

[0021] When the stretching and chucking device 7′, 7″ according to FIG.3 is released, the camshaft 1 returns in the direction of its originalposition shown in FIG. 1 due to the release and its elasticity, so thatits outside diameter D4 increases again in the direction of the outsidediameter D1. In doing so, the cam 2 is permanently secured in themounting site 4 both axially and in a torsionally fixed manner by apress fit. The stretching and chucking device can then be removed.

[0022] According to FIG. 4, it is also conceivable to provide athreading area 6″ on a chucking element 7″ which acts on the insidecircumference of the camshaft 1, instead of the threading area beinglocated on the camshaft 1 (FIGS. 1 through 3) or to provide a threadingarea on two such chucking elements. In this case, the components and/orcams 2 to be mounted on the camshaft 1 are arranged on the threadingarea 6″, the diameter of which is preferably smaller than the insidediameter of the inside opening 3 of the components and/or cams 2, beforepositioning the chucking element 7″. After the stretching, then thecomponents and/or cams 2 are pushed onto the camshaft 1 and brought intothe predetermined position.

[0023] To permit the threading area 6″ to be pushed onto the camshaft 1,it preferably has an approach ramp 8 which forms a transition from thediameter D3″ of the threading area 6″ to the diameter D4 of thestretched camshaft 1.

[0024] It is also pointed out that it is conceivable to use a shaft 1having the original diameter D1, which is subsequently reduced indrawing to the diameter D4, only in the area of the mounting site(s) 4.The other shaft areas then have a diameter smaller than D1. These shaftareas are also reduced in drawing.

1. A method of manufacturing a worked shaft, whereby at least onecomponent (2) is placed on the shaft (1), in particular a cam beingplaced on a camshaft, whereby the shaft (1) is introduced into anopening (3) in the component (1), whereby, before mounting the component(2), the shaft (1) is stretched with the help of a stretching andchucking device (7′, 7″) such that an original diameter (D1) in the areaof at least one mounting site (4) is reduced to a diameter (D4); thenthe component (2) is pushed onto the shaft (1) and is shifted to themounting site (4) on the shaft (1) and next the stretching and chuckingdevice (7′, 7″) is released again, whereupon the diameter of the shaft(1) enlarges again in the direction of the original diameter (D1),characterized in that the shaft (1) is reduced by the stretching andchucking device (7′, 7″) to a diameter (D4) which is slightly largerthan the inside diameter (D2) of the opening (3) of the component (2),and the component (2) is displaced to the mounting site (4) with a forceacting on the shaft (1).
 2. Method according to claim 1, characterizedin that the shaft (1) has in an edge area a threading area (6) in whichat least one component (2) is situated, and after stretching the shaft(1) by the stretching and chucking device (7′, 7″), the component (2) ispushed out of the threading area (6) and onto the stretched shaft (1)and then is shifted to the mounting site (4) on the stretched shaft (1).3. Method according to claim 1 or 2, characterized in that thestretching and chucking device (7′, 7″) has at least one chuckingelement (7″) which acts on the inside circumference of a shaft (1) whichis designed to be at least partially hollow.
 4. Method according toclaim 3, characterized in that the chucking element (7″) which acts onthe inside circumference of the shaft (1) has a threading area (6″) onwhich is arranged at least one component (2), and the component (2) ispushed out of the threading area (6″) of the chucking element (7″) andonto the shaft (1) after the stretching of the shaft (1) and then isshifted on the shaft (1) to the mounting site (4).
 5. Method accordingto one of claims 1 through 4, characterized in that a stretching andchucking device (7′, 7″) is used, having a chucking element (7′) whichacts on the outside circumference of the shaft (1) and a chuckingelement (7″) which acts on the inside circumference of a shaft (1) thatis designed to be at least partially hollow.
 6. Method according to oneof claims 1 through 5, characterized in that a stretching and chuckingdevice (7′, 7″) which has two chucking elements (7″) acting on theinside circumference of a shaft (1) which is designed to be at leastpartially hollow is used.
 7. Method according to one of claims 1 through6, characterized in that the chucking element (7″) of the stretching andchucking device (7′, 7″) acting on the inside circumference of the shaft(1) has an area with an outside thread which is screwed onto an insidethread situated in the inside circumference of a shaft (1) which isdesigned to be at least partially hollow.
 8. Method according to one ofclaims 1 through 7, characterized in that the area of the shaft (1)facing the threading area (6″) of the chucking element (7″) acting onthe inside circumference of the shaft (1) has an approach ramp (8) forthe component (2).
 9. Method according to one of claims 1 through 8,characterized in that the shaft (1) is a solid shaft.
 10. Methodaccording to one of claims 1 through 9, characterized in that the shaft(1) is a hollow shaft.
 11. Method according to one of claims 1 through10, characterized in that a lubricant is supplied for shifting thecomponent (2) on the shaft (1) into the area between the component (2)and the shaft (1).
 12. Method according to one of claims 1 through 11,characterized in that a shaft having the original diameter (D1)essentially along its total length is used.
 13. Method according to oneof claims 1 through 11, characterized in that a shaft having theoriginal diameter (D1) essentially only in the area of its at least onemounting site (4) and having a diameter smaller than the originaldiameter (D1) in the other areas of the shaft is used.